It is well known that contact lenses can be used to improve vision. Various contact lenses have been commercially produced for many years. Early designs of contact lenses were fashioned from hard materials. Although these lenses are still currently used in some applications, they are not suitable for all patients due to their poor comfort and relatively low permeability to oxygen. Later developments in the field gave rise to soft contact lenses, based upon hydrogels.
Hydrogel contact lenses are very popular today. These lenses are often more comfortable to wear than contact lenses made of hard materials. Soft contact lenses can be manufactured by forming a lens in a multi-part mold where the combined parts form a topography consistent with the desired final lens.
Ophthalmic lenses are often made by cast molding, in which a monomer material is deposited in a cavity defined between optical surfaces of opposing mold parts. Multi-part molds used to fashion hydrogels into a useful article, such as an ophthalmic lens, can include for example, a first mold part with a convex portion that corresponds with a back curve of an ophthalmic lens and a second mold part with a concave portion that corresponds with a front curve of the ophthalmic lens. It is to be understood that unless specifically indicated otherwise, a first mold part can also include front curve mold part wherein the second mold part will therefore comprise a back curve mold part.
To prepare a lens using such mold parts, an uncured hydrogel lens formulation is placed between the concave and convex surfaces of the mold portions and subsequently cured. The hydrogel lens formulation may be cured, for example by exposure to either, or both, heat and light. The cured hydrogel forms a lens according to the dimensions of the mold portions.
Following cure, traditional practice dictates that the mold portions are separated and the lens remains adhered to one of the mold portions. A release process detaches the lens from the remaining mold part.
Further, new developments in the field have led to contact lenses made from hydrogels and silicone hydrogels that are coated with polymers to improve the comfort of the lenses. Often lenses are coated by treating the cured lenses with a polymer. Recently polymer coated lenses have been produced by coating the surfaces of a two part mold with a polymer, adding an uncured formulation to the coated lens mold, curing the lens, and subsequently releasing the cured lens from the mold where the surface of said cured lens is coated with the polymer that was originally adhered to the surface of the mold
A particular problem, however, is that the monomer or reaction mixture is supplied in excess to the concave mold piece. Upon mating of the molds, thereby defining the lens, the excess monomer or monomer mixture is expelled from the mold cavity and rests on or between the flange of one or both mold pieces forming an annular ring or flashing around the formed lens.
After separating the two-mold pieces, the peripheral flashing of now polymerized excess material usually remains with the female mold piece, the same piece that holds the lens. In order to further process the lens through hydration, inspection, packaging, sterilization, etc., it is necessary to remove the flashing of polymerized material from the female mold piece. When the flashing remains with the female mold piece with the lens, it is manually picked off with the finger.
Therefore it would be useful to have improved methods and apparatus for removing an ophthalmic lens from the mold in which it is held, and also remove any surrounding flashing from the lens.